Laser systems utilizing fiber bundles for power delivery and beam switching

ABSTRACT

In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by coupling the laser beam into an optical fiber of a fiber bundle and directing the laser beam onto one or more in-coupling locations on the input end of the optical fiber. The beam emitted at the output end of the optical fiber may be utilized to process a workpiece.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/429,270, filed Dec. 2, 2016, the entiredisclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

In various embodiments, the present invention relates to laser systems,specifically laser systems with multiple outputs and controllable beamprofiles, e.g., variable beam parameter products.

BACKGROUND

High-power laser systems are utilized for a host of differentapplications, such as welding, cutting, drilling, and materialsprocessing. Such laser systems typically include a laser emitter, thelaser light from which is coupled into an optical fiber (or simply a“fiber”), and an optical system that focuses the laser light from thefiber onto the workpiece to be processed. Wavelength beam combining(WBC) is a technique for scaling the output power and brightness fromlaser diodes, laser diode bars, stacks of diode bars, or other lasersarranged in a one- or two-dimensional array. WBC methods have beendeveloped to combine beams along one or both dimensions of an array ofemitters. Typical WBC systems include a plurality of emitters, such asone or more diode bars, that are combined using a dispersive element toform a multi-wavelength beam. Each emitter in the WBC systemindividually resonates, and is stabilized through wavelength-specificfeedback from a common partially reflecting output coupler that isfiltered by the dispersive element along a beam-combining dimension.Exemplary WBC systems are detailed in U.S. Pat. No. 6,192,062, filed onFeb. 4, 2000, U.S. Pat. No. 6,208,679, filed on Sep. 8, 1998, U.S. Pat.No. 8,670,180, filed on Aug. 25, 2011, and U.S. Pat. No. 8,559,107,filed on Mar. 7, 2011, the entire disclosure of each of which isincorporated by reference herein.

Optical systems for laser systems are typically engineered to producethe highest-quality laser beam, or, equivalently, the beam with thelowest beam parameter product (BPP). The BPP is the product of the laserbeam's divergence angle (half-angle) and the radius of the beam at itsnarrowest point (i.e., the beam waist, the minimum spot size). That is,BPP=NA×D/2, where D is the focusing spot (the waist) diameter and NA isthe numerical aperture; thus, the BPP may be varied by varying NA and/orD. The BPP quantifies the quality of the laser beam and how well it canbe focused to a small spot, and is typically expressed in units ofmillimeter-milliradians (mm-mrad). A Gaussian beam has the lowestpossible BPP, given by the wavelength of the laser light divided by pi.The ratio of the BPP of an actual beam to that of an ideal Gaussian beamat the same wavelength is denoted M², which is a wavelength-independentmeasure of beam quality.

In many laser-processing applications, the desired beam spot size,divergence, and beam quality may vary depending on, for example, thetype of processing and/or the type of material being processed. This isparticularly true for industrial lasers in material processingapplications. For example, a lower BPP value, i.e., a better beamquality, may be preferred for cutting a thin metal, while a larger BPP(i.e., a worse beam quality) may be preferred for cutting throughthicker metals. In order to make such changes to the BPP of the lasersystem, frequently the output optical system or the optical fiber mustbe swapped out with other components and/or realigned, a time-consumingand expensive process that may even lead to inadvertent damage of thefragile optical components of the laser system. Thus, there is a needfor alternative techniques for varying the BPP of a laser system that donot involve such adjustments to the laser beam or optical system at theoutput of the optical fiber. In addition, there is a need for lasersystems having multiple output beams with variable BPP, thereby enablingthe sharing of the laser system among different workstations.

SUMMARY

In accordance with embodiments of the present invention, laser systemsproduce output beams that are directed into one or more optical fibersof a fiber bundle for output to any of multiple discrete locations. Oneor more of the optical fibers of the fiber bundle may be multi-cladfibers, i.e., incorporate a central core region with multiple claddingregions concentrically surrounding the core region. In otherembodiments, one or more of the optical fibers may be single-cladfibers, i.e., have only one cladding region surrounding the core region.In various embodiments, different optical fibers in the fiber bundlehave different core diameters. One or more of the fibers in the fiberbundle may have multiple discrete core regions. In accordance withvarious embodiments, the laser output beam is directed into a particularfiber of the fiber bundle and/or into one or more specificcross-sectional regions of the fiber (e.g., the core region and/or oneor more of the cladding regions) in order to vary the beam shape and/orthe BPP of the output beam.

As utilized herein, changing the “shape” of a laser beam refers toaltering the cross-sectional profile and dimension(s) of the beam (e.g.,at a point at which the beam intersects a surface). Changes in shape maybe accompanied by changes in beam size, angular intensity distributionof the beam, and BPP, but mere changes in beam BPP are not necessarilysufficient to change laser beam shape and vice versa.

Output beams produced in accordance with embodiments of the presentinvention may be utilized to process a workpiece such that the surfaceof the workpiece is physically altered and/or such that a feature isformed on or within the surface, in contrast with optical techniquesthat merely probe a surface with light (e.g., reflectivitymeasurements). Exemplary processes in accordance with embodiments of theinvention include cutting, welding, drilling, and soldering. Variousembodiments of the invention may also process workpieces at one or morespots or along a one-dimensional linear or curvilinear processing path,rather than flooding all or substantially all of the workpiece surfacewith radiation from the laser beam. Such one-dimensional paths may becomposed of multiple segments, each of which may be linear orcurvilinear.

One advantage of variable shape and/or BPP is improved laser applicationperformance for different types of processing techniques or differenttypes of materials being processed. Embodiments of the invention mayalso utilize various techniques for varying BPP and/or shape of laserbeams described in U.S. patent application Ser. No. 14/632,283, filed onFeb. 26, 2015, U.S. patent application Ser. No. 14/747,073, filed Jun.23, 2015, U.S. patent application Ser. No. 14/852,939, filed Sep. 14,2015, U.S. patent application Ser. No. 15/188,076, filed Jun. 21, 2016,U.S. patent application Ser. No. 15/479,745, filed Apr. 5, 2017, andU.S. patent application Ser. No. 15/649,841, filed Jul. 14, 2017, thedisclosure of each of which is incorporated in its entirety herein byreference.

Herein, “optical elements” may refer to any of lenses, mirrors, prisms,gratings, and the like, which redirect, reflect, bend, or in any othermanner optically manipulate electromagnetic radiation. Herein, beamemitters, emitters, or laser emitters, or lasers include anyelectromagnetic beam-generating device such as semiconductor elements,which generate an electromagnetic beam, but may or may not beself-resonating. These also include fiber lasers, disk lasers, non-solidstate lasers, etc. Generally, each emitter includes a back reflectivesurface, at least one optical gain medium, and a front reflectivesurface. The optical gain medium increases the gain of electromagneticradiation that is not limited to any particular portion of theelectromagnetic spectrum, but that may be visible, infrared, and/orultraviolet light. An emitter may include or consist essentially ofmultiple beam emitters such as a diode bar configured to emit multiplebeams. The input beams received in the embodiments herein may besingle-wavelength or multi-wavelength beams combined using varioustechniques known in the art. In addition, references to “lasers,” “laseremitters,” or “beam emitters” herein include not only single-diodelasers, but also diode bars, laser arrays, diode bar arrays, and singleor arrays of vertical cavity surface-emitting lasers (VCSELs).

Embodiments of the invention may be utilized with wavelength beamcombining (WBC) systems that include a plurality of emitters, such asone or more diode bars, that are combined using a dispersive element toform a multi-wavelength beam. Each emitter in the WBC systemindividually resonates, and is stabilized through wavelength-specificfeedback from a common partially reflecting output coupler that isfiltered by the dispersive element along a beam-combining dimension.Exemplary WBC systems are detailed in U.S. Pat. No. 6,192,062, filed onFeb. 4, 2000, U.S. Pat. No. 6,208,679, filed on Sep. 8, 1998, U.S. Pat.No. 8,670,180, filed on Aug. 25, 2011, and U.S. Pat. No. 8,559,107,filed on Mar. 7, 2011, the entire disclosure of each of which isincorporated by reference herein. Multi-wavelength output beams of WBCsystems may be utilized as input beams in conjunction with embodimentsof the present invention for, e.g., BPP, shape, and/or polarizationcontrol.

In an aspect, embodiments of the invention feature a laser system havingmultiple outputs. The system includes, consists essentially of, orconsists of a beam emitter for emission of a laser beam, a fiber bundle,a reflector and/or an optical element, and a controller. The fiberbundle includes, consists essentially of, or consists of a plurality ofoptical fibers. Each of the optical fibers has (i) an input end forreceiving a laser beam, and (ii) opposite the input end, an output endfor delivery of the received laser beam to a workpiece. The reflectorand/or the optical element may receive the laser beam and couple thelaser beam into one or more (e.g., only one) of the input ends of theoptical fibers in the fiber bundle. For example, the reflector mayreceive the laser beam and reflect the laser beam toward the fiberbundle, and the optical element may receive the laser beam from thereflector and couple the laser beam into one or more (e.g., only one) ofthe input ends of an optical fiber in the fiber bundle. The controllercauses and controls relative motion between the input ends of theoptical fibers and the reflector and/or the optical element to therebydetermine (i) the optical fiber(s) of the fiber bundle into which thelaser beam is coupled and/or (ii) a location at which the laser beam isdirected on an end face of one or more selected fibers, whereby a beamshape and/or a beam parameter product is determined at least in part bythe coupling of the laser beam into the optical fiber(s).

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The controller may be configured forfeedback operation to progressively adjust the location at which thelaser beam is directed on the end face of the selected fiber based on ameasured parameter. The measured parameter may be a measured parameterof the workpiece (e.g., composition, thickness, height or depth of asurface feature, reflectivity, etc.) and/or of the laser beam (e.g.,flux density, beam shape, beam diameter, beam intensity, beam intensityas a function of areal beam location, etc.). The relative motion betweenthe input ends of the optical fibers and the reflector and/or theoptical element may include, consist essentially of, or consist ofrotation of the reflector, rotation of the optical element, translationof the reflector, translation of the optical element, rotation of theinput ends of the optical fibers, and/or translation of the input endsof the optical fibers. The optical element may include, consistessentially of, or consist of one or more lenses, one or more gratings(e.g., diffraction gratings), and/or one or more prisms. One or morephysical characteristics of at least two of the optical fibers in thefiber bundle may be different. The physical characteristic may include,consist essentially of, or consist of a quantity of fiber cores, aquantity of cladding regions, a diameter of a fiber core, a thickness ofa cladding region, a refractive index of a fiber core, and/or arefractive index of a cladding region. The system may include an inputend cap. One or more of the input ends of the optical fiber in the fiberbundle may be fused to or otherwise optically coupled to the input endcap. An output end cap may be disposed on, fused to, and/or opticallycoupled to the output end of one or more of the optical fibers. Eachoptical fiber may have a different output end cap.

At least one of the optical fibers may include, consist essentially of,or consist of a multi-clad optical fiber having multiple claddingssurrounding one or more fiber cores. For example, the multi-clad opticalfiber may include, consist essentially of, or consist of a fiber core, afirst cladding region surrounding the fiber core, and a second claddingregion surrounding the first cladding region. The refractive index ofthe fiber core may be larger than a refractive index of the firstcladding region. The refractive index of the first cladding region maybe larger than a refractive index of the second cladding region. Thecontroller may be configured to, for the optical fiber of the fiberbundle into which the laser beam is coupled, control relative motionbetween the input ends of the optical fibers and the reflector and/orthe optical element to thereby determine one or more portions of theoptical fiber into which the laser beam is coupled. The portions of theoptical fiber may include, consist essentially of, or consist of thefiber core, the first cladding region, and the second cladding region.The portions of the optical fiber may include, consist essentially of,or consist of, more generally, one or more fiber cores and/or one ormore cladding regions.

At least one of the optical fibers may include, consist essentially of,or consist of a step-clad optical fiber including, consistingessentially of, or consisting of (i) a central core having a firstrefractive index, (ii) surrounding the central core, a first claddinghaving a second refractive index, (iii) surrounding the first cladding,an annular core having a third refractive index, and (iv) surroundingthe annular core, a second cladding having a fourth refractive index.The first refractive index may be larger than the fourth refractiveindex. The third refractive index may be larger than the fourthrefractive index. The second refractive index may be smaller than thefirst refractive index and larger than the fourth refractive index. Thecontroller may be configured to, for the optical fiber of the fiberbundle into which the laser beam is coupled, control relative motionbetween the input ends of the optical fibers and the reflector and/orthe optical element to thereby determine one or more portions of theoptical fiber into which the laser beam is coupled. The portions of theoptical fiber may include, consist essentially of, or consist of thecentral core, the first cladding, and the annular core. The portions ofthe optical fiber may include, consist essentially of, or consist of thecentral core and the first cladding. The portions of the optical fibermay include, consist essentially of, or consist of the central core, thefirst cladding, the annular core, and the second cladding. The portionsof the optical fiber may include, consist essentially of, or consist ofthe first cladding and the annular core. The portions of the opticalfiber may include, consist essentially of, or consist of the firstcladding, the annular core, and the second cladding.

The beam emitter may be responsive to the controller. The controller maybe configured to modulate an output power of the beam emitter duringrelative motion between the input ends of the optical fibers and thereflector and/or the optical element. The controller may be configuredto not modulate an output power of the beam emitter during relativemotion between the input ends of the optical fibers and the reflectorand/or the optical element. The controller may be configured to increasethe beam parameter product of the laser beam by coupling at least aportion of the laser beam into one or more cladding regions of theoptical fiber(s) into which the laser beam is coupled. The controllermay be configured to determine the beam shape and/or the beam parameterproduct based at least in part on a characteristic of the workpieceproximate the output end of the optical fiber into which the laser beamis coupled. The characteristic of the workpiece may include, consistessentially of, or consist of a thickness of the workpiece and/or acomposition of the workpiece. The system may include a memory,accessible to the controller, for storing data corresponding to aprocessing path defined on the workpiece. The path may include at leastone directional change. The path may be composed of one or more linearsegments and/or one or more curvilinear segments. The controller may beconfigured to alter the output power, beam shape, and/or beam parameterproduct of the beam along the processing path. The memory may be atleast in part resident in the controller and/or at least in partresident remotely (e.g., network storage, cloud storage, etc.). Thesystem may include a database for storing processing data for aplurality of materials. The controller may be configured to query thedatabase to obtain processing data for one or more materials of theworkpiece. The beam shape and/or the beam parameter product of the beammay be determined at least in part by the obtained processing data.

The beam emitter may include, consist essentially of, or consist of oneor more beam sources emitting a plurality of discrete beams, focusingoptics for focusing the plurality of beams onto a dispersive element, adispersive element for receiving and dispersing the received focusedbeams, and a partially reflective output coupler positioned to receivethe dispersed beams, transmit a portion of the dispersed beamstherethrough as the laser beam, and reflect a second portion of thedispersed beams back toward the dispersive element. The laser beam maybe composed of multiple wavelengths. Each of the discrete beams may havea different wavelength. The second portion of the dispersed beams maypropagate back to the one or more beam sources to thereby stabilize thebeams to their emission wavelengths. The focusing optics may include orconsist essentially of one or more cylindrical lenses, one or morespherical lenses, one or more spherical mirrors, and/or one or morecylindrical mirrors. The dispersive element may include, consistessentially of, or consist of one or more diffraction gratings (e.g.,one or more transmissive gratings and/or one or more reflectivegratings), one or more dispersive fibers, and/or one or more prisms.

In another aspect, embodiments of the invention feature a method ofadjusting a beam parameter product and/or a beam shape of a laser beam.A fiber bundle is provided. The fiber bundle includes, consistsessentially of, or consists of a plurality of optical fibers. Each ofthe optical fibers has (i) an input end for receiving a laser beam, and(ii) opposite the input end, an output end for delivery of the receivedlaser beam. A laser beam is directed toward a selected one or more ofthe optical fibers of the fiber bundle. Thereduring and/or thereafter,the beam parameter product and/or the beam shape of the laser beam isselected by directing the laser beam onto one or more first in-couplinglocations on the input end(s) of the selected optical fiber(s).

Embodiments of the invention may include one or more of the following inany of a variety of combinations. One or more workpieces disposedproximate the output end(s) of the selected optical fiber(s) may beprocessed with the laser beam. The beam parameter product and/or thebeam shape of the laser beam may be selected based at least in part of acharacteristic of one or more of the workpieces. The characteristic ofthe workpiece may include, consist essentially of, or consist of athickness of the workpiece and/or a composition of the workpiece. Atleast one of the first in-coupling locations may intersect a claddingregion of a selected optical fiber. Directing the laser beam toward theselected one of the optical fibers may include, consist essentially of,or consist of (i) reflecting the laser beam with one or more reflectorsand/or (ii) focusing the laser beam with one or more optical elements.One or more physical characteristics of at least two of the opticalfibers in the fiber bundle may be different. The physical characteristicmay include, consist essentially of, or consist of a quantity of fibercores, a quantity of cladding regions, a diameter of a fiber core, athickness of a cladding region, a refractive index of a fiber core,and/or a refractive index of a cladding region.

At least one of the optical fibers may include, consist essentially of,or consist of a multi-clad optical fiber having multiple claddingssurrounding one or more fiber cores. For example, the multi-clad opticalfiber may include, consist essentially of, or consist of a fiber core, afirst cladding region surrounding the fiber core, and a second claddingregion surrounding the first cladding region. The refractive index ofthe fiber core may be larger than a refractive index of the firstcladding region. The refractive index of the first cladding region maybe larger than a refractive index of the second cladding region.

At least one of the optical fibers may include, consist essentially of,or consist of a step-clad optical fiber including, consistingessentially of, or consisting of (i) a central core having a firstrefractive index, (ii) surrounding the central core, a first claddinghaving a second refractive index, (iii) surrounding the first cladding,an annular core having a third refractive index, and (iv) surroundingthe annular core, a second cladding having a fourth refractive index.The first refractive index may be larger than the fourth refractiveindex. The third refractive index may be larger than the fourthrefractive index. The second refractive index may be smaller than thefirst refractive index and larger than the fourth refractive index.

The beam parameter product and/or the beam shape of the laser beam maybe altered by directing the laser beam onto one or more secondin-coupling locations on the input end of the selected optical fiberand/or one or more other optical fibers in the fiber bundle. The one ormore second in-coupling locations may be different from the one or morefirst in-coupling locations. The laser beam may be emitted from a beamemitter including, consisting essentially of, or consisting of one ormore beam sources emitting a plurality of discrete beams, focusingoptics for focusing the plurality of beams onto a dispersive element, adispersive element for receiving and dispersing the received focusedbeams, and a partially reflective output coupler positioned to receivethe dispersed beams, transmit a portion of the dispersed beamstherethrough as the laser beam, and reflect a second portion of thedispersed beams back toward the dispersive element. The laser beam maybe composed of multiple wavelengths. Each of the discrete beams may havea different wavelength. The second portion of the dispersed beams maypropagate back to the one or more beam sources to thereby stabilize thebeams to their emission wavelengths. The focusing optics may include orconsist essentially of one or more cylindrical lenses, one or morespherical lenses, one or more spherical mirrors, and/or one or morecylindrical mirrors. The dispersive element may include, consistessentially of, or consist of one or more diffraction gratings (e.g.,one or more transmissive gratings and/or one or more reflectivegratings), one or more dispersive fibers, and/or one or more prisms.

In yet another aspect, embodiments of the invention feature a method ofprocessing a plurality of workpieces using output beams having differentcharacteristics and originating from the same input beam. A fiber bundleis provided. The fiber bundle includes, consists essentially of, orconsists of a first optical fiber and a second optical fiber. The firstoptical fiber has (a) a first input end for receiving a laser beam and(b) opposite the first input end, a first output end for delivery of thelaser beam to a first workpiece. The second optical fiber has (a) forreceiving the laser beam, a second input end proximate the first inputend, and (b) opposite the second input end, a second output end fordelivery of the laser beam to a second workpiece different from thefirst workpiece. In various embodiments, the first and second outputends deliver the laser beam to different portions of the same workpiece.The laser beam is directed toward the first input end to process thefirst workpiece. Before and/or during the processing of the firstworkpiece, a first beam parameter product and/or a first beam shape ofthe laser beam is selected by directing the laser beam onto one or morefirst in-coupling locations on the first input end. The laser beam isdirected toward the second input end to process the second workpiece.Before and/or during the processing of the second workpiece, a secondbeam parameter product and/or a second beam shape of the laser beam isselected by directing the laser beam onto one or more second in-couplinglocations on the second input end. The second beam parameter productand/or the second beam shape may be different from the first beamparameter product and/or the first beam shape. The second beam parameterproduct and/or the second beam shape may be the same as the first beamparameter product and/or the first beam shape.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. At least one characteristic of thefirst and second workpieces may be different. The at least onecharacteristic may include, consist essentially of, or consist ofthickness and/or composition. The output power of the laser beam may bemodulated between directing the laser beam toward the first input endand directing the laser beam toward the second input end. The outputpower of the laser beam may not be modulated between directing the laserbeam toward the first input end and directing the laser beam toward thesecond input end. An interior configuration of the first optical fibermay be substantially identical to an interior configuration of thesecond optical fiber. At least one of the first in-coupling locationsmay intersect one or more cladding regions of the first optical fiber,and beam energy coupled into the one or more cladding regions may beutilized to process the first workpiece. At least one of the secondin-coupling locations may intersect one or more cladding regions of thesecond optical fiber, and beam energy coupled into the one or morecladding regions may be utilized to process the second workpiece.Directing the laser beam toward the first input end may include, consistessentially of, or consist of (i) reflecting the laser beam with one ormore reflectors and/or (ii) focusing the laser beam with one or moreoptical elements. Directing the laser beam toward the second input endmay include, consist essentially of, or consist of (i) reflecting thelaser beam with one or more reflectors and/or (ii) focusing the laserbeam with one or more optical elements. A physical characteristic of thefirst optical fiber and the second optical fiber may be different. Thephysical characteristic may include, consist essentially of, or consistof a quantity of fiber cores, a quantity of cladding regions, a diameterof a fiber core, a thickness of a cladding region, a refractive index ofa fiber core, and/or a refractive index of a cladding region.

The first optical fiber and/or the second optical fiber may include,consist essentially of, or consist of a multi-clad optical fiber havingmultiple claddings surrounding one or more fiber cores. For example, themulti-clad optical fiber may include, consist essentially of, or consistof a fiber core, a first cladding region surrounding the fiber core, anda second cladding region surrounding the first cladding region. Therefractive index of the fiber core may be larger than a refractive indexof the first cladding region. The refractive index of the first claddingregion may be larger than a refractive index of the second claddingregion.

The first optical fiber and/or the second optical fiber may include,consist essentially of, or consist of a step-clad optical fiberincluding, consisting essentially of, or consisting of (i) a centralcore having a first refractive index, (ii) surrounding the central core,a first cladding having a second refractive index, (iii) surrounding thefirst cladding, an annular core having a third refractive index, and(iv) surrounding the annular core, a second cladding having a fourthrefractive index. The first refractive index may be larger than thefourth refractive index. The third refractive index may be larger thanthe fourth refractive index. The second refractive index may be smallerthan the first refractive index and larger than the fourth refractiveindex.

The laser beam may be emitted from a beam emitter including, consistingessentially of, or consisting of one or more beam sources emitting aplurality of discrete beams, focusing optics for focusing the pluralityof beams onto a dispersive element, a dispersive element for receivingand dispersing the received focused beams, and a partially reflectiveoutput coupler positioned to receive the dispersed beams, transmit aportion of the dispersed beams therethrough as the laser beam, andreflect a second portion of the dispersed beams back toward thedispersive element. The laser beam may be composed of multiplewavelengths. Each of the discrete beams may have a different wavelength.The second portion of the dispersed beams may propagate back to the oneor more beam sources to thereby stabilize the beams to their emissionwavelengths. The focusing optics may include or consist essentially ofone or more cylindrical lenses, one or more spherical lenses, one ormore spherical mirrors, and/or one or more cylindrical mirrors. Thedispersive element may include, consist essentially of, or consist ofone or more diffraction gratings (e.g., one or more transmissivegratings and/or one or more reflective gratings), one or more dispersivefibers, and/or one or more prisms.

In another aspect, embodiments of the invention feature a method ofprocessing a workpiece with a laser beam. A fiber bundle is provided.The fiber bundle includes, consists essentially of, or consists of aplurality of optical fibers. Each of the optical fibers has (i) an inputend for receiving a laser beam, and (ii) opposite the input end, anoutput end for delivery of the received laser beam. A workpiece isdisposed proximate the output end of a selected one of the opticalfibers. A beam parameter product and/or a beam shape for processing ofthe workpiece is determined based on at least one characteristic of theworkpiece. A laser beam is directed toward the selected optical fiber.While the laser beam is being directed toward the selected opticalfiber, the laser beam is directed onto one or more in-coupling locationson the input end of the selected optical fiber to select the beamparameter product and/or the beam shape of the laser beam emitted fromthe output end of the selected optical fiber. The workpiece is processedwith the laser beam emitted from the output end of the selected opticalfiber.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. Processing the workpiece may include,consist essentially of, or consist of physically altering at least aportion of and/or forming a feature on and/or in a surface of theworkpiece. Processing the workpiece may include, consist essentially of,or consist of cutting, welding, etching, annealing, drilling, soldering,and/or brazing. The at least one characteristic of the workpiece mayinclude, consist essentially of, or consist of a thickness of theworkpiece and/or a composition of the workpiece. At least one of thein-coupling locations may intersect one or more cladding regions of theselected optical fiber, and beam energy coupled into the one or morecladding regions may be utilized to process the workpiece. Directing thelaser beam toward the selected optical fiber may include, consistessentially of, or consist of (i) reflecting the laser beam with one ormore reflectors and/or (ii) focusing the laser beam with one or moreoptical elements. A physical characteristic of at least two of theoptical fibers in the fiber bundle may be different. The physicalcharacteristic may include, consist essentially of, or consist of aquantity of fiber cores, a quantity of cladding regions, a diameter of afiber core, a thickness of a cladding region, a refractive index of afiber core, and/or a refractive index of a cladding region.

The selected optical fiber may include, consist essentially of, orconsist of a multi-clad optical fiber having multiple claddingssurrounding one or more fiber cores. For example, the multi-clad opticalfiber may include, consist essentially of, or consist of a fiber core, afirst cladding region surrounding the fiber core, and a second claddingregion surrounding the first cladding region. The refractive index ofthe fiber core may be larger than a refractive index of the firstcladding region. The refractive index of the first cladding region maybe larger than a refractive index of the second cladding region.

The selected optical fiber may include, consist essentially of, orconsist of a step-clad optical fiber including, consisting essentiallyof, or consisting of (i) a central core having a first refractive index,(ii) surrounding the central core, a first cladding having a secondrefractive index, (iii) surrounding the first cladding, an annular corehaving a third refractive index, and (iv) surrounding the annular core,a second cladding having a fourth refractive index. The first refractiveindex may be larger than the fourth refractive index. The thirdrefractive index may be larger than the fourth refractive index. Thesecond refractive index may be smaller than the first refractive indexand larger than the fourth refractive index.

The beam parameter product and/or the beam shape of the laser beam maybe altered while or after processing the workpiece by directing thelaser beam onto one or more second in-coupling locations on the inputend of the selected optical fiber and/or one or more other opticalfibers in the fiber bundle. The one or more second in-coupling locationsmay be different from the one or more first in-coupling locations. Thelaser beam may be emitted from a beam emitter including, consistingessentially of, or consisting of one or more beam sources emitting aplurality of discrete beams, focusing optics for focusing the pluralityof beams onto a dispersive element, a dispersive element for receivingand dispersing the received focused beams, and a partially reflectiveoutput coupler positioned to receive the dispersed beams, transmit aportion of the dispersed beams therethrough as the laser beam, andreflect a second portion of the dispersed beams back toward thedispersive element. The laser beam may be composed of multiplewavelengths. Each of the discrete beams may have a different wavelength.The second portion of the dispersed beams may propagate back to the oneor more beam sources to thereby stabilize the beams to their emissionwavelengths. The focusing optics may include or consist essentially ofone or more cylindrical lenses, one or more spherical lenses, one ormore spherical mirrors, and/or one or more cylindrical mirrors. Thedispersive element may include, consist essentially of, or consist ofone or more diffraction gratings (e.g., one or more transmissivegratings and/or one or more reflective gratings), one or more dispersivefibers, and/or one or more prisms.

These and other objects, along with advantages and features of thepresent invention herein disclosed, will become more apparent throughreference to the following description, the accompanying drawings, andthe claims. Furthermore, it is to be understood that the features of thevarious embodiments described herein are not mutually exclusive and mayexist in various combinations and permutations. As used herein, the term“substantially” means ±10%, and in some embodiments, ±5%. The term“consists essentially of” means excluding other materials thatcontribute to function, unless otherwise defined herein. Nonetheless,such other materials may be present, collectively or individually, intrace amounts. Herein, the terms “radiation” and “light” are utilizedinterchangeably unless otherwise indicated. Herein, “downstream” or“optically downstream,” is utilized to indicate the relative placementof a second element that a light beam strikes after encountering a firstelement, the first element being “upstream,” or “optically upstream” ofthe second element. Herein, “optical distance” between two components isthe distance between two components that is actually traveled by lightbeams; the optical distance may be, but is not necessarily, equal to thephysical distance between two components due to, e.g., reflections frommirrors or other changes in propagation direction experienced by thelight traveling from one of the components to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1A is a schematic diagram of a laser system incorporating a fiberbundle of multiple optical fibers in accordance with various embodimentsof the invention;

FIG. 1B is a schematic cross-sectional diagram of the fiber bundle ofFIG. 1A;

FIG. 1C is a schematic cross-sectional diagram of a step-clad opticalfiber in accordance with various embodiments of the invention;

FIG. 1D is a schematic graph of the relative refractive indices ofportions of the step-clad optical fiber of FIG. 1C;

FIG. 2A is a schematic diagram of a laser system incorporating a fiberbundle of multiple optical fibers in accordance with various embodimentsof the invention;

FIG. 2B is a schematic cross-sectional diagram of the fiber bundle ofFIG. 2A;

FIG. 3 is a schematic cross-sectional diagram of a multi-clad opticalfiber, and a graph of the relative refractive indices of portions of themulti-clad optical fiber, in accordance with various embodiments of theinvention;

FIG. 4 is an exemplary sequence of beam shapes and BPPs as a function ofapplied beam-positioning voltage in accordance with various embodimentsof the invention;

FIG. 5 is a graph of beam in-coupling position as a function of controlvoltage in accordance with various embodiments of the invention; and

FIG. 6 is a schematic diagram of a wavelength beam combining lasersystem that may be utilized to supply the input beam for laser beamdelivery systems in accordance with various embodiments of theinvention.

DETAILED DESCRIPTION

FIG. 1A depicts a laser system 100 in accordance with variousembodiments of the present invention. As shown, a laser beam 110 (whichmay be, e.g., the output beam of a WBC system) is directed by areflector 120 (e.g., one or more mirrors) and coupled by an opticalelement 130 (e.g., one or more lenses) into one of multiple fibers of afiber bundle 140, which includes, consists essentially of, or consistsof two or more optical fibers 150, at least two (or even all) of whichmay have different internal configurations (e.g., numbers of claddinglayers, number of cores, refractive indices of cores and/or claddings,sizes of cores and/or claddings, etc.). Each of the optical fibers 150of the fiber bundle 140 is connected to a different laser head 160 (thefour laser heads 160 in FIG. 1A are labeled as laser heads 160-1, 160-2,160-3, and 160-n; embodiments of the invention may include as few as twolaser heads 160 or more than four laser heads 160) that may include, forexample, further optics for directing the output laser beam toward aworkpiece for materials processing such as cutting, welding, etc. FIG.1A depicts an exemplary embodiment in which the laser beam 110 is beingcoupled to either laser head 160-1 or laser head 160-2 via movement(e.g., rotation and/or translation) of the reflector 120. The laser beam110 may be directed toward one or more of the fibers 150 of fiber bundle140 by other means in addition to or instead of reflector 120; forexample, movement of the optical element 130, the use of one or moreadjustable optical elements such as prisms, etc. In various embodimentsof the invention, the fibers 150 of the fiber bundle 140 may bemulti-mode fibers, and the core diameters of such fibers may be, e.g.,at least 20 μm. FIG. 1B depicts a schematic end-on view of the fiberbundle 140. Although FIG. 1B depicts the fibers of the fiber bundlearranged in a close-packed, round configuration, embodiments of theinvention also include other arrangements of the fibers within the fiberbundle, e.g., linear.

During operation of the laser system 100, the power of the laser beam110 may be decreased or the laser beam 110 may be turned off or directedto a component other than fiber bundle 140 (e.g., a beam dump to discardor dissipate the beam energy) during at least a portion of the timeperiod during which the laser beam 110 is directed from one of thefibers 150 to another. In various embodiments of the invention, in orderto reduce the risk of damage to the fibers 150, the input side of thefiber bundle 140 is attached (e.g., via fusion) to a glass endcap. Thatis, the input side of the fiber bundle may be a unitary segment withinwhich the different fibers 150 are coupled to different areal portionsof the glass endcap. As shown in FIG. 1B, the fibers, at least at theinput end of fiber bundle 140, may be disposed within a sheath 170. Theoutput side of each fiber 150 may also be fused to an individual glassendcap. The glass endcaps (not shown in FIG. 1A) may have lengths of,e.g., at least 5 mm. The lengths of the endcaps may be, e.g., 50 mm orless.

In accordance with various embodiments of the invention, the variouscore and cladding layers of optical fibers in fiber bundles may include,consist essentially of, or consist of glass, such as substantially purefused silica and/or fused silica doped with fluorine, titanium,germanium, and/or boron. Selection of proper materials to achieve thedesired refractive indices in different portions of the optical fibers(e.g., core and cladding regions) may be performed by those of skill inthe art without undue experimentation.

In various embodiments, the laser system 100 may output multiple beamssubstantially simultaneously via rapid steering of the laser beam 110among two or more fibers 150; in such embodiments, multiple laser heads160 may be utilized for materials processing simultaneously. Embodimentsof the invention provide a convenient way to deliver laser beams havingdifferent BPPs and/or beam shapes to different workstations and/orworkpieces. For example, the fiber bundle 140 may include fibers 150having different core diameters. In an example embodiment, the fiberbundle 140 incorporates optical fibers having different core diametersranging from 100 μm to 600 μm, and thereby produces laser beams havingBPP values ranging from ˜4 to ˜24 mm·mrad. These values are merelyexemplary, and embodiments of the invention may be utilized to produceoutput laser beams having a wide range of BPPs and/or beam shapes,depending upon the configuration(s) of the fibers 150 within fiberbundle 140.

In various embodiments of the invention, the laser system 100incorporates a controller 180 that controls the movement of the laserbeam 110 among the various fibers 150 of the fiber bundle 140. Forexample, the controller 180 may control the movement (e.g., rotationand/or translation with respect to one, two or three degrees of freedom)of reflector 120, the optical element 130, and/or the fiber bundle 140in order to cause the laser beam 110 to be directed into a differentfiber 150 or a different portion of a fiber 150 in fiber bundle 140. Forexample, the reflector 120 and/or the optical element 130 may be movedvia one or more piezoelectric actuators controlled by the controller180. These actuators may incorporate stepper motors that incrementallyrotate and/or translate a controlled element so as to bring the beaminto a desired position. The controller 180 may also move the input endsof the fibers 150 of fiber bundle 140, in addition to or instead ofcontrolling reflector 120 and/or optical element 130, in order to couplethe laser beam 110 into different fibers 150 and/or different portionsof a single fiber 150. The controller 180 may compute a proper positionof a laser beam relative to a fiber end face based on a desired value ofa beam property (e.g., flux density, beam diameter, beam shape, etc.) atthe workpiece and a known relationship between the beam property and theposition of the beam relative to a fiber end face or the mostappropriate fiber in the bundle to carry the beam; or based on userinput (e.g., a commanded degree of overlap with or position on adesignated fiber's end face or a portion thereof (e.g., one or morecores or claddings)); or, as explained in greater detail below, may usefeedback so that the optimal alignment between the beam and the end faceof a designated fiber is progressively attained. For example, aphotodetector or other light sensor may be utilized proximate theworkpiece to monitor the beam shape, beam diameter, and/or flux densityat the workpiece surface (for example, the beam property of the beamitself, or via measurement of a reflection from the workpiece surface),and the controller may utilize the measured value(s) as feedback toadjust the positioning of the input beam relative to the selected fiberend until the desired beam property is achieved at the workpiece. Othersensors may be utilized in addition or instead of light sensors inembodiments of the invention, e.g., thermal sensors and/or sensorsmeasuring the effect of the beam on the workpiece surface (e.g., depthor profile sensors, etc.).

The controller 180 may also control the laser beam 110 before, during,or after the movement of the laser beam 110 relative to the fiber bundle140; for example, the controller 180 may modulate the output power ofthe laser beam 110 and/or switch the laser beam 110 on or off during oneor more (or even all) of the motion of the laser beam 110 relative tothe fiber bundle 140.

The controller 180 may be provided as either software, hardware, or somecombination thereof. For example, the controller 180 may be implementedon one or more conventional server-class computers, such as a PC havinga CPU board containing one or more processors such as the Pentium orCeleron family of processors manufactured by Intel Corporation of SantaClara, Calif., the 680x0 and POWER PC family of processors manufacturedby Motorola Corporation of Schaumburg, Ill., and/or the ATHLON line ofprocessors manufactured by Advanced Micro Devices, Inc., of Sunnyvale,Calif. Thus, in various embodiments the controller 180 may include aprocessor (e.g., a central processing unit). The processor may alsoinclude a main memory unit for storing programs and/or data relating tothe methods described above. The memory may include random access memory(RAM), read only memory (ROM), and/or FLASH memory residing on commonlyavailable hardware such as one or more application specific integratedcircuits (ASIC), field programmable gate arrays (FPGA), electricallyerasable programmable read-only memories (EEPROM), programmableread-only memories (PROM), programmable logic devices (PLD), orread-only memory devices (ROM). In some embodiments, the programs may beprovided using external RAM and/or ROM such as optical disks, magneticdisks, as well as other commonly used storage devices. For embodimentsin which the functions are provided as one or more software programs,the programs may be written in any of a number of high level languagessuch as PYTHON, FORTRAN, PASCAL, JAVA, C, C++, C#, BASIC, variousscripting languages, and/or HTML. Additionally, the software may beimplemented in an assembly language directed to the microprocessorresident on a target computer; for example, the software may beimplemented in Intel 80x86 assembly language if it is configured to runon an IBM PC or PC clone. The software may be embodied on an article ofmanufacture including, but not limited to, a floppy disk, a jump drive,a hard disk, an optical disk, a magnetic tape, a PROM, an EPROM, EEPROM,field-programmable gate array, or CD-ROM. Control software implementingbeam alignment with a desired spatial position and feedback-responsivemovement is well-characterized in the scanner and plotter art.

Embodiments of the present invention may also utilize multi-clad opticalfibers in the fiber bundle to provide control over the shape and/or BPPof the laser beam coupled into the fibers. For example, laser systems inaccordance with embodiments of the invention may utilize step-cladoptical fibers as detailed in U.S. patent application Ser. No.15/479,745, filed on Apr. 5, 2017 (“the '745 application”), the entiredisclosure of which is incorporated by reference herein. FIG. 1C is across-sectional schematic diagram of an example step-clad optical fiber190 that may be utilized in fiber bundles in accordance with embodimentsof the present invention. In accordance with various embodiments,step-clad fiber 190 includes, consists essentially of, or consists of acenter core 192, a first cladding 194, an annular core 196, and a secondcladding 198. As set forth in the '745 application, various propertiesof the first cladding 194 enable BPP variation based at least in part onthe power coupled into the first cladding 194. Other BPP and/or beamshape variations may be achieved based on power coupled into otherportions of step-clad optical fiber 190, either in addition to orinstead of first cladding 194. FIG. 1D depicts the refractive index andradius of each layer of the step-clad fiber 190. As shown, therefractive index (N₂) of the first cladding 194 of the fiber 190 has avalue between a high index N₁ and a low index N₃, so that the centercore 192 will have a smaller NA, given by sqrt(N₁ ²−N₂ ²), than the NAof the annular core 196, given by sqrt(N₁ ²−N₃ ²). While FIG. 1D depictsthe indices of refraction of the center core 192 and the annular core196 as being approximately equal to each other, in various embodimentsthe index of refraction of the annular core 196 may be different from(i.e., either less than or greater than) the index of refraction of thecenter core 192; however, in general, the index of refraction of theannular core 196 remains larger than the index of refraction of thefirst cladding 194. In various embodiments, as disclosed in the '745application, the annular core 196 may have the same refractive index asthe first cladding 194, i.e., the annular core 196 depicted in FIGS. 1Cand 1D merges into the first cladding 194. Step-clad fibers 190 inaccordance with embodiments of the invention may have substantially allor all of the laser power coupled into the first cladding 194. Morepower coupled into the first cladding 194 will generally lead to largerBPP. In various embodiments, the diameter ratio of the first cladding194 and the center core 192 is larger than 1.2, e.g., between 1.2 and 3,or even between 1.3 and 2.

FIG. 2A depicts a laser system 100 in which laser beam 110 is directedto a fiber bundle 140 that includes multiple multi-clad optical fibers200. As shown and as detailed above, coupling of the laser beam 110 intothe various optical fibers may be performed via movement of reflector120 and/or optical element 130 under direction of the controller 180.

In various embodiments of the invention, the laser beam 110 may beswitched among different fibers in fiber bundle 140 having differentstructures, e.g., different core diameters, different claddingdiameters, different numbers of claddings, etc. Such switching mayinvolve the movement of the laser beam 110 along a distance 210 from onefiber to another, as shown in FIG. 2B. In various embodiments, theproperties (e.g., BPP) of the laser beam 110 may also be controlled viacoupling of the laser beam 110 into different portions of a singleoptical fiber within the fiber bundle 140; such movements may, forexample, couple beam power from the laser beam 110 into one or moredifferent portions (e.g., cores and/or claddings) of the optical fiber.For example, FIG. 2B depicts the movement along a distance 220 of thelaser beam 110 between the core region and a cladding region of a singleoptical fiber, a shorter distance than distance 210.

Two or more of the optical fibers within the fiber bundle 140 may havesubstantially identical interior configurations, i.e., have the sameinternal structures in terms of numbers, locations, and refractiveindices of cores and claddings. The lengths of optical fibers havingsubstantially identical interior configurations may be different inorder to accommodate different distances between the input ends of theoptical fibers and the output ends of the optical fibers. That is, thedistances between the input end of the fiber bundle and the laser headscoupled to different otherwise internally identical optical fibers maybe different.

FIG. 3 schematically depicts the structure and refractive index profileof an exemplary multi-clad fiber 200 that may be utilized in lasersystems in accordance with embodiments of the invention. As shown, themulti-clad fiber 200 may have a core region 300 concentricallysurrounded by a first cladding layer 310 and a second cladding layer320. The fiber 200 may also have additional glass and/or polymer layers(not shown) for, e.g., mechanical support disposed outside of the secondcladding layer 320. The index of refraction of the various regions ofthe multi-clad fiber 200 may decrease stepwise from the core 300 to thefirst cladding layer 310 to the second cladding layer 320, as shown inFIG. 3. In various embodiments, the core region 300 may have a diameterbetween 50 μm and 200 μm, e.g., approximately 100 μm. The thickness (or,in various embodiments, diameter) of the first cladding region 310 mayrange between, for example, 200 μm and 600 μm, e.g., approximately 400μm to approximately 480 μm.

In various embodiments, movement of the laser beam 110 such that it iscoupled into (a) the core region 300, (b) the first cladding region 310,or (c) both alters the BPP of the output beam. For example, FIG. 4depicts various BPPs and beam shapes at the output end of a multi-cladoptical fiber having a 100 μm core diameter and a first cladding layerof 480 μm diameter (i.e., the first cladding layer surrounds the core,and the outer boundary of the first cladding layer is 480 μm from thecenter of the fiber) for a 4 kW WBC laser beam coupled into the fibervia rotation of a reflector 120 controlled by a piezoelectric actuatorvia a voltage signal ranging from 0 to 10 V. As shown, the BPP of thelaser beam ranges between 4 and 20, and the shape of the beam may becontrolled to have one, two, or more distinct peaks. FIG. 5 is a graphillustrating the relationship between the voltage signal applied to apiezoelectric actuator configured for translational movement of the beamrelative to the fiber end face and the approximate location on thecross-section of the multi-clad optical fiber at which the laser beam110 is coupled. As shown in FIGS. 4 and 5, as the laser beam 110 iscoupled increasingly off-center into the core and/or at least partiallyinto the first cladding layer, the BPP of the resulting output beamtends to increase. In the situation depicted in FIGS. 4 and 5, the inputbeam has a diameter of about 95 μm; thus, the laser beam 110 begins tooverlap the first cladding layer at voltages greater than about 0.5 V.In addition, the beam shape transitions from a single peak to a splitnarrow peak to a relatively flat broader peak to a double-peak shape.The input beam position may be varied while the input beam is operatedat a substantially constant power, and thus the beam BPP and/or shapemay transition smoothly from one value to another. In other embodiments,the power of the input beam may be decreased or turned off entirely asthe beam position is moved (and then increased back to a desired level,which may or may not be substantially equal to the beam power prior tomovement, after the beam is moved), and thus the beam BPP and/or shapemay be altered discontinuously from one value to another.

Embodiments of the invention utilize such input beam movements within asingle fiber to adjust output beam BPP and/or shape. Embodiments of theinvention also utilize input beam movements among different opticalfibers within a fiber bundle to provide such output beams withadjustable BPP and/or shape to different laser heads, as shown in FIGS.1A and 2A. The different laser heads may be utilized to processdifferent workpieces and may be physically located in differentlocations (e.g., different rooms or workstations in a processingfacility). The controller 180 may, in accordance with the embodiments ofthe invention, control the BPP and/or beam shape of the output beambased on the type of desired processing (e.g., cutting, welding, etc.)and/or on one or more characteristics (e.g., materials parameters,thickness, material type, etc.) of the workpiece to be processed and/orof a desired processing path mapped out for the output beam. Suchprocess and/or material parameters may be selected by a user from astored database in a memory associated with controller 180 or may beentered via an input device (e.g., touchscreen, keyboard, pointingdevice such as a computer mouse, etc.). One or more processing paths maybe provided by a user and stored in an onboard or remote memoryassociated with controller 180. After workpiece and/or processing pathselection, the controller 180 queries the database to obtain thecorresponding parameter values. The stored values may include a BPPand/or beam shape suitable to the material and/or to one or moreprocessing paths or processing locations on the material.

As is well understood in the plotting and scanning art, the requisiterelative motion between the beam and the desired beam path may beproduced, as discussed above, by optical deflection of the beam using amovable mirror, physical movement of the laser using a gantry,lead-screw or other arrangement, and/or a mechanical arrangement formoving the workpiece rather than (or in addition to) the beam. Thecontroller 180 may, in some embodiments, receive feedback regarding theposition and/or processing efficacy of the beam relative to theworkpiece from a feedback unit connected to suitable monitoring sensors.In response to signals from the feedback unit, the controller 180 mayalter the path, BPP and/or shape of the beam via, e.g., movement of theinput beam 110 to one or more different locations within an opticalfiber in a fiber bundle 140. Embodiments of the invention may alsoincorporate aspects of the apparatus and techniques disclosed in U.S.patent application Ser. No. 14/639,401, filed on Mar. 5, 2015, U.S.patent application Ser. No. 15/261,096, filed on Sep. 9, 2016, and U.S.patent application Ser. No. 15/649,841, filed on Jul. 14, 2017, theentire disclosure of each of which is incorporated by reference herein.

In addition, the laser system may incorporate one or more systems fordetecting the thickness of the workpiece and/or heights of featuresthereon. For example, the laser system may incorporate systems (orcomponents thereof) for interferometric depth measurement of theworkpiece, as detailed in U.S. patent application Ser. No. 14/676,070,filed on Apr. 1, 2015, the entire disclosure of which is incorporated byreference herein. Such depth or thickness information may be utilized bythe controller to control the output beam BPP and/or shape to optimizethe processing (e.g., cutting or welding) of the workpiece, e.g., inaccordance with records in the database corresponding to the type ofmaterial being processed.

Laser systems and laser delivery systems in accordance with embodimentsof the present invention and detailed herein may be utilized in and/orwith WBC laser systems. Specifically, in various embodiments of theinvention, multi-wavelength output beams of WBC laser systems may beutilized as the input beams for laser beam delivery systems forvariation of BPP and/or beam shape as detailed herein. FIG. 6 depicts anexemplary WBC laser system 600 that utilizes one or more lasers 605. Inthe example of FIG. 6, laser 605 features a diode bar having four beamemitters emitting beams 610 (see magnified input view 615), butembodiments of the invention may utilize diode bars emitting any numberof individual beams or two-dimensional arrays or stacks of diodes ordiode bars. In view 615, each beam 610 is indicated by a line, where thelength or longer dimension of the line represents the slow divergingdimension of the beam, and the height or shorter dimension representsthe fast diverging dimension. A collimation optic 620 may be used tocollimate each beam 610 along the fast dimension. Transform optic(s)625, which may include, consist essentially of, or consist of one ormore cylindrical or spherical lenses and/or mirrors, are used to combineeach beam 610 along a WBC direction 630. The transform optics 625 thenoverlap the combined beam onto a dispersive element 635 (which mayinclude, consist essentially of, or consist of, e.g., a reflective ortransmissive diffraction grating, a dispersive prism, a grism(prism/grating), a transmission grating, or an Echelle grating), and thecombined beam is then transmitted as single output profile onto anoutput coupler 640. The output coupler 640 then transmits the combinedbeams 645 as shown on the output front view 650. The output coupler 640is typically partially reflective and acts as a common front facet forall the laser elements in this external cavity system 600. An externalcavity is a lasing system where the secondary mirror is displaced at adistance away from the emission aperture or facet of each laser emitter.In some embodiments, additional optics are placed between the emissionaperture or facet and the output coupler or partially reflectivesurface. The output beam 645 is a thus a multiple-wavelength beam(combining the wavelengths of the individual beams 610), and may beutilized as the input beam in laser beam delivery systems detailedherein and/or may be coupled into an optical fiber.

The terms and expressions employed herein are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:
 1. A laser system having multiple output fibers, thesystem comprising: a beam emitter for emission of a laser beam; a fiberbundle comprising a plurality of optical fibers, each of the opticalfibers having (i) an input end for receiving the laser beam, and (ii)opposite the input end, an output end for delivery of the received laserbeam to a workpiece; a reflector for receiving the laser beam andreflecting the laser beam toward the fiber bundle; an optical elementfor receiving the laser beam from the reflector and coupling the laserbeam into only one of the input ends of an optical fiber in the fiberbundle; and a controller for causing and controlling relative motionbetween the input ends of the optical fibers and at least one of thereflector or the optical element to thereby determine at least one of(i) the optical fiber of the fiber bundle into which the laser beam iscoupled or (ii) a location at which the laser beam is directed on an endface of a selected fiber, whereby at least one of a beam shape or a beamparameter product is determined at least in part by the optical fiberinto which the laser beam is coupled and/or by the location at which thelaser beam is directed on the end face of the selected fiber, whereinthe controller is configured to, for the optical fiber of the fiberbundle into which the laser beam is coupled, control relative motionbetween the input ends of the optical fibers and at least one of thereflector or the optical element to thereby determine one or moreportions of the optical fiber into which the laser beam is coupled, theportions of the optical fiber comprising one or more fiber cores and oneor more cladding regions.
 2. The system of claim 1, wherein thecontroller is configured for feedback operation to progressively adjustthe location at which the laser beam is directed on the end face of theselected fiber based on a measured parameter.
 3. The system of claim 2,wherein the measured parameter is a measured parameter of the workpiece.4. The system of claim 2, wherein the measured parameter is a measuredparameter of the laser beam.
 5. The system of claim 1, wherein therelative motion between the input ends of the optical fibers and atleast one of the reflector or the optical element comprises at least oneof rotation of the reflector or lateral translation of the opticalelement.
 6. The system of claim 1, wherein the optical element comprisesone or more lenses and/or one or more prisms.
 7. The system of claim 1,wherein a physical characteristic of at least two of the optical fibersin the fiber bundle is different.
 8. The system of claim 7, wherein thephysical characteristic comprises a quantity of fiber cores, a quantityof cladding regions, a diameter of a fiber core, a thickness of acladding region, a refractive index of a fiber core, and/or a refractiveindex of a cladding region.
 9. The system of claim 1, further comprisingan input end cap, wherein the input ends of the optical fibers in thefiber bundle are fused to the input end cap.
 10. The system of claim 1,further comprising, for each optical fiber, an output end cap disposedon the output end of the optical fiber.
 11. The system of claim 1,wherein at least one of the optical fibers comprises a multi-cladoptical fiber comprising a fiber core, a first cladding regionsurrounding the fiber core, and a second cladding region surrounding thefirst cladding region.
 12. The system of claim 11, wherein (i) arefractive index of the fiber core is larger than a refractive index ofthe first cladding region, and (ii) the refractive index of the firstcladding region is larger than a refractive index of the second claddingregion.
 13. The system of claim 1, wherein: the beam emitter isresponsive to the controller; and the controller is configured tomodulate an output power of the beam emitter during relative motionbetween the input ends of the optical fibers and the at least one of thereflector or the optical element.
 14. The system of claim 1, wherein thecontroller is configured to increase the beam parameter product of thelaser beam by coupling at least a portion of the laser beam into acladding region of the optical fiber into which the laser beam iscoupled.
 15. The system of claim 1, wherein the controller is configuredto determine the at least one of the beam shape or the beam parameterproduct based at least in part on a characteristic of the workpieceproximate the output end of the optical fiber into which the laser beamis coupled.
 16. The system of claim 15, wherein the characteristic ofthe workpiece comprises at least one of a thickness of the workpiece ora composition of the workpiece.
 17. The system of claim 15, furthercomprising (i) a memory, accessible to the controller, for storing datacorresponding to a processing path defined on the workpiece, and (ii) adatabase for storing processing data for a plurality of materials,wherein the controller is configured to query the database to obtainprocessing data for one or more materials of the workpiece, the at leastone of the beam shape or the beam parameter product of the beam beingdetermined at least in part by the obtained processing data.
 18. Thesystem of claim 1, wherein the beam emitter comprises: one or more beamsources emitting a plurality of discrete beams; focusing optics forfocusing the plurality of beams onto a dispersive element; a dispersiveelement for receiving and dispersing the received focused beams; and apartially reflective output coupler positioned to receive the dispersedbeams, transmit a portion of the dispersed beams therethrough as thelaser beam, and reflect a second portion of the dispersed beams backtoward the dispersive element, wherein the laser beam is composed ofmultiple wavelengths.
 19. The system of claim 18, wherein the dispersiveelement comprises a diffraction grating.
 20. The system of claim 11,wherein the determined one or more portions of the optical fiber intowhich the laser beam is coupled comprise the fiber core, the firstcladding region, and the second cladding region.
 21. The system of claim1, wherein at least one of the optical fibers comprises a step-cladoptical fiber comprising (i) a central core having a first refractiveindex, (ii) surrounding the central core, a first cladding having asecond refractive index, (iii) surrounding the first cladding, anannular core having a third refractive index, and (iv) surrounding theannular core, a second cladding having a fourth refractive index,wherein (i) the first refractive index is larger than the fourthrefractive index, (ii) the third refractive index is larger than thefourth refractive index, and (iii) the second refractive index issmaller than the first refractive index and larger than the fourthrefractive index.
 22. The system of claim 21, wherein the determined oneor more portions of the optical fiber into which the laser beam iscoupled comprise the central core, the first cladding, and the annularcore.
 23. A laser system having multiple output fibers, the systemcomprising: a beam emitter for emission of a laser beam; a fiber bundlecomprising a plurality of optical fibers, each of the optical fibershaving (i) an input end for receiving the laser beam, and (ii) oppositethe input end, an output end for delivery of the received laser beam toa workpiece, wherein at least one of the optical fibers comprises amulti-clad optical fiber comprising a fiber core, a first claddingregion surrounding the fiber core, and a second cladding regionsurrounding the first cladding region; a reflector for receiving thelaser beam and reflecting the laser beam toward the fiber bundle; anoptical element for receiving the laser beam from the reflector andcoupling the laser beam into only one of the input ends of an opticalfiber in the fiber bundle; and a controller for causing and controllingrelative motion between the input ends of the optical fibers and atleast one of the reflector or the optical element to thereby determineat least one of (i) the optical fiber of the fiber bundle into which thelaser beam is coupled or (ii) a location at which the laser beam isdirected on an end face of a selected fiber, whereby at least one of abeam shape or a beam parameter product is determined at least in part bythe optical fiber into which the laser beam is coupled and/or by thelocation at which the laser beam is directed on the end face of theselected fiber, wherein the controller is configured to, for the opticalfiber of the fiber bundle into which the laser beam is coupled, controlrelative motion between the input ends of the optical fibers and atleast one of the reflector or the optical element to thereby determineone or more portions of the optical fiber into which the laser beam iscoupled, the portions of the optical fiber comprising the fiber core,the first cladding region, and the second cladding region.
 24. Thesystem of claim 23, wherein the controller is configured for feedbackoperation to progressively adjust the location at which the laser beamis directed on the end face of the selected fiber based on a measuredparameter.
 25. The system of claim 24, wherein the measured parameter isa measured parameter of the workpiece.
 26. The system of claim 24,wherein the measured parameter is a measured parameter of the laserbeam.
 27. The system of claim 23, wherein the relative motion betweenthe input ends of the optical fibers and at least one of the reflectoror the optical element comprises at least one of rotation of thereflector or lateral translation of the optical element.
 28. The systemof claim 23, wherein the optical element comprises one or more lensesand/or one or more prisms.
 29. The system of claim 23, wherein aphysical characteristic of at least two of the optical fibers in thefiber bundle is different.
 30. The system of claim 29, wherein thephysical characteristic comprises a quantity of fiber cores, a quantityof cladding regions, a diameter of a fiber core, a thickness of acladding region, a refractive index of a fiber core, and/or a refractiveindex of a cladding region.
 31. The system of claim 23, furthercomprising an input end cap, wherein the input ends of the opticalfibers in the fiber bundle are fused to the input end cap.
 32. Thesystem of claim 23, further comprising, for each optical fiber, anoutput end cap disposed on the output end of the optical fiber.
 33. Thesystem of claim 23, wherein (i) a refractive index of the fiber core islarger than a refractive index of the first cladding region, and (ii)the refractive index of the first cladding region is larger than arefractive index of the second cladding region.
 34. The system of claim23, wherein at least one of the optical fibers comprises a step-cladoptical fiber comprising (i) a central core having a first refractiveindex, (ii) surrounding the central core, a first cladding having asecond refractive index, (iii) surrounding the first cladding, anannular core having a third refractive index, and (iv) surrounding theannular core, a second cladding having a fourth refractive index,wherein (i) the first refractive index is larger than the fourthrefractive index, (ii) the third refractive index is larger than thefourth refractive index, and (iii) the second refractive index issmaller than the first refractive index and larger than the fourthrefractive index.
 35. The system of claim 23, wherein: the beam emitteris responsive to the controller; and the controller is configured tomodulate an output power of the beam emitter during relative motionbetween the input ends of the optical fibers and the at least one of thereflector or the optical element.
 36. The system of claim 23, whereinthe controller is configured to increase the beam parameter product ofthe laser beam by coupling at least a portion of the laser beam into acladding region of the optical fiber into which the laser beam iscoupled.
 37. The system of claim 23, wherein the controller isconfigured to determine the at least one of the beam shape or the beamparameter product based at least in part on a characteristic of theworkpiece proximate the output end of the optical fiber into which thelaser beam is coupled.
 38. The system of claim 37, wherein thecharacteristic of the workpiece comprises at least one of a thickness ofthe workpiece or a composition of the workpiece.
 39. The system of claim37, further comprising (i) a memory, accessible to the controller, forstoring data corresponding to a processing path defined on theworkpiece, and (ii) a database for storing processing data for aplurality of materials, wherein the controller is configured to querythe database to obtain processing data for one or more materials of theworkpiece, the at least one of the beam shape or the beam parameterproduct of the beam being determined at least in part by the obtainedprocessing data.
 40. The system of claim 23, wherein the beam emittercomprises: one or more beam sources emitting a plurality of discretebeams; focusing optics for focusing the plurality of beams onto adispersive element; a dispersive element for receiving and dispersingthe received focused beams; and a partially reflective output couplerpositioned to receive the dispersed beams, transmit a portion of thedispersed beams therethrough as the laser beam, and reflect a secondportion of the dispersed beams back toward the dispersive element,wherein the laser beam is composed of multiple wavelengths.
 41. Thesystem of claim 40, wherein the dispersive element comprises adiffraction grating.
 42. A laser system having multiple output fibers,the system comprising: a beam emitter for emission of a laser beam; afiber bundle comprising a plurality of optical fibers, each of theoptical fibers having (i) an input end for receiving the laser beam, and(ii) opposite the input end, an output end for delivery of the receivedlaser beam to a workpiece; a reflector for receiving the laser beam andreflecting the laser beam toward the fiber bundle; an optical elementfor receiving the laser beam from the reflector and coupling the laserbeam into only one of the input ends of an optical fiber in the fiberbundle; and a controller for causing and controlling relative motionbetween the input ends of the optical fibers and at least one of thereflector or the optical element to thereby determine at least one of(i) the optical fiber of the fiber bundle into which the laser beam iscoupled or (ii) a location at which the laser beam is directed on an endface of a selected fiber, whereby at least one of a beam shape or a beamparameter product is determined at least in part by the optical fiberinto which the laser beam is coupled and/or by the location at which thelaser beam is directed on the end face of the selected fiber, wherein atleast one of the optical fibers comprises a step-clad optical fibercomprising (i) a central core having a first refractive index, (ii)surrounding the central core, a first cladding having a secondrefractive index, (iii) surrounding the first cladding, an annular corehaving a third refractive index, and (iv) surrounding the annular core,a second cladding having a fourth refractive index, wherein (i) thefirst refractive index is larger than the fourth refractive index, (ii)the third refractive index is larger than the fourth refractive index,and (iii) the second refractive index is smaller than the firstrefractive index and larger than the fourth refractive index.
 43. Thesystem of claim 42, wherein the controller is configured to, for theoptical fiber of the fiber bundle into which the laser beam is coupled,control relative motion between the input ends of the optical fibers andat least one of the reflector or the optical element to therebydetermine one or more portions of the optical fiber into which the laserbeam is coupled, the portions of the optical fiber comprising thecentral core, the first cladding, and the annular core.
 44. The systemof claim 42, wherein the controller is configured for feedback operationto progressively adjust the location at which the laser beam is directedon the end face of the selected fiber based on a measured parameter. 45.The system of claim 44, wherein the measured parameter is a measuredparameter of the workpiece.
 46. The system of claim 44, wherein themeasured parameter is a measured parameter of the laser beam.
 47. Thesystem of claim 42, wherein the relative motion between the input endsof the optical fibers and at least one of the reflector or the opticalelement comprises at least one of rotation of the reflector or lateraltranslation of the optical element.
 48. The system of claim 42, whereinthe optical element comprises one or more lenses and/or one or moreprisms.
 49. The system of claim 42, wherein a physical characteristic ofat least two of the optical fibers in the fiber bundle is different. 50.The system of claim 49, wherein the physical characteristic comprises aquantity of fiber cores, a quantity of cladding regions, a diameter of afiber core, a thickness of a cladding region, a refractive index of afiber core, and/or a refractive index of a cladding region.
 51. Thesystem of claim 42, further comprising an input end cap, wherein theinput ends of the optical fibers in the fiber bundle are fused to theinput end cap.
 52. The system of claim 42, further comprising, for eachoptical fiber, an output end cap disposed on the output end of theoptical fiber.
 53. The system of claim 42, wherein at least one of theoptical fibers comprises a multi-clad optical fiber comprising a fibercore, a first cladding region surrounding the fiber core, and a secondcladding region surrounding the first cladding region.
 54. The system ofclaim 42, wherein: the beam emitter is responsive to the controller; andthe controller is configured to modulate an output power of the beamemitter during relative motion between the input ends of the opticalfibers and the at least one of the reflector or the optical element. 55.The system of claim 42, wherein the controller is configured to increasethe beam parameter product of the laser beam by coupling at least aportion of the laser beam into a cladding region of the optical fiberinto which the laser beam is coupled.
 56. The system of claim 42,wherein the controller is configured to determine the at least one ofthe beam shape or the beam parameter product based at least in part on acharacteristic of the workpiece proximate the output end of the opticalfiber into which the laser beam is coupled.
 57. The system of claim 56,wherein the characteristic of the workpiece comprises at least one of athickness of the workpiece or a composition of the workpiece.
 58. Thesystem of claim 56, further comprising (i) a memory, accessible to thecontroller, for storing data corresponding to a processing path definedon the workpiece, and (ii) a database for storing processing data for aplurality of materials, wherein the controller is configured to querythe database to obtain processing data for one or more materials of theworkpiece, the at least one of the beam shape or the beam parameterproduct of the beam being determined at least in part by the obtainedprocessing data.
 59. The system of claim 42, wherein the beam emittercomprises: one or more beam sources emitting a plurality of discretebeams; focusing optics for focusing the plurality of beams onto adispersive element; a dispersive element for receiving and dispersingthe received focused beams; and a partially reflective output couplerpositioned to receive the dispersed beams, transmit a portion of thedispersed beams therethrough as the laser beam, and reflect a secondportion of the dispersed beams back toward the dispersive element,wherein the laser beam is composed of multiple wavelengths.
 60. Thesystem of claim 59, wherein the dispersive element comprises adiffraction grating.